This invention relates to improved tape guidance in a magnetic tape data cartridge.
Magnetic tape cartridges for magnetic tape carrying digital data on a number of tracks across the tape are well known. Tape cartridges include a cartridge shell that defines an enclosure, and a pair of tape reels supported within the enclosure. A length of magnetic tape extends along a tape path within the enclosure. Each end of the tape is wound onto one of the reels. The tape moves past suitable guides and across an opening in an edge of the cartridge into which a read/write head or transducer protrudes to tension the tape and write or read data when the cartridge is inserted into a recording/reproducing machine. The tape is driven by a belt so that the lineal tape speed is controlled precisely. Tape speeds are now in the range of 20 inches per second to 120 inches per second.
In order to maintain the tape properly positioned so that each of the very narrow individual tracks of data is appropriately positioned as it crosses the read/write head, it is important that the tape be guided precisely along its path of travel.
It is desirable to increase the density of the data tracks on a one-quarter inch tape, utilizing a standard belt driven cartridge. The present invention aids in achieving increased density.
Servo-drives are also used for positioning a tape under positive control, but such drives are expensive. The present invention aids in reducing the band width of tape control in servo-drives as well as reducing the complexity, and thus cost, of such drives.
Magnetic tape cartridges of the type disclosed in, for example, U.S. Pat. No. 5,104,058, provide precisely located reference surfaces in the form of flanged guide pins for positioning an edge of the tape relative to the head, at selected points along its path, and means for urging the tape into engagement with the flanges so as to position the tape, and hence the tracks of recorded data relative to the head. The function of urging the tape into engagement with the guide pin flanges results from the angle at which the flanged guide pins are inserted into the baseplate. By inserting at least one of the guide pins into the baseplate with a slight deviation from perpendicularity with the baseplate, a steering effect which urges the tape into engagement with particular flanges of the guide pins is provided to guide the data tracks relative to the head.
Flanged cylindrical tape guides have the additional advantage being able to be manufactured to a high degree of precision, since they can be produced on an automatic lathe, or screw machine.
A multiple roller tape guidance system which provides an arcuate path further is disclosed in U.S. Pat. No. 5,173,828. Three rollers on each side of the transducer are provided to guide the tape in its path.
A tape guide which engages the edges of the tape over a longer distance, thereby enabling a lubricating air film to form, so as to reduce frictional drag on the tape, is disclosed in EP 536 912, assigned to Minnesota Mining and Manufacturing Co. In addition, the longer engagement length serves to damp out vibrations and other transport deviations which might otherwise result from conditions upstream from the guide, such as tape reel and other transport rollers eccentricities.
The tape guide also must be highly abrasion resistant, since magnetic recording tape is inherently abrasive. In IBM Technical Disclosure Bulletin Vol. 29, No. 5, October, 1986, wear resistant pads are used to contact the edge of the tape in a compliant guide system, thereby enabling the material for the spring portion of the compliant guide to be chosen without trading off spring properties for wear properties.
Surface coatings for imparting wear resistance to surfaces which might not otherwise resist wear are known. U.S. Pat. No. 4,594,772, for example, discloses a hard anodize coating which is resistant to wear caused by transport of magnetic tape.
In addition, dry lubricants can be incorporated into wear resistant anodized coatings for the purpose of reducing friction. Such coatings are used in the present invention and are described in the following references:
Seitzinger, R. C., "Coatings that Cut Friction," MACHINE DESIGN, Oct. 21, 1976, pp. 114-119. PA1 Covino, C. P., "Hard Coat Plus Solid Lube Fights Wear Problems, " METAL PROGRESS, June, 1975, pp. 69-70.
The present invention provides an elongated guide that stabilized a magnetic tape as it is moved in a path in a belt driven tape cartridge. The elongated support aids in maintaining the data tracks on the tape properly aligned.